Occupational therapist Cathy Kleinman-Barnett works with breast cancer patients, but she has never encouraged women with lymphedema, a breast cancer-related swelling of the arm, to lift weights.

A new study contradicts recommendations that breast cancer survivors avoid weight lifting, because of swelling.

However, she may be changing her tune, thanks to a new study in the August 13 issue of the New England Journal of Medicine. It turns out that breast cancer survivors with lymphedema who engage in a progressive, supervised weight-lifting program fare better than their counterparts who do not lift weights.

Lymphedema occurs in as many as 70 percent of women who have breast cancer surgery. Sometimes lymph nodes in the armpit are removed for cancer testing, which can cause the clear fluid (lymph) that circulates in the body to build up in the affected limb. As a result, women must wear a compression sleeve and glove during waking hours.

"For so long, we were taught no heavy lifting and no resistance for our patients, but this article is shouting out yes to resistance and weight," says Kleinman-Barnett, who is a lymphedema specialist at Northwest Medical Center in Margate, Florida. "The benefits seem to outweigh the risks, and a weight-lifting program may help these women prevent injuries from everyday tasks by boosting strength in the affected limbs." Health.com: Fit at any age: Your 50s strength workout

Oftentimes breast cancer survivors were told to steer clear of weight lifting -- or even carrying their children or heavy grocery bags, because doctors thought it could worsen the swelling. The new study, the largest to date, seems to contradict that recommendation.

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In fact, the research team led by Kathryn Schmitz, an associate professor of epidemiology and biostatistics at the University of Pennsylvania, in Philadelphia, and a member of the university's Abramson Cancer Center, found that weight lifting increased muscle strength, decreased the number and severity of arm and hand symptoms, and reduced lymphedema exacerbations.

"Our study shows that participating in a safe, structured weight-lifting routine can help women with lymphedema take control of their symptoms and reap the many rewards that resistance training has on their overall health," says Schmitz. Resistance training helps build bone density and can improve health in general. Health.com: How to spot symptoms of breast cancer that has spread

In the new study, 141 women with lymphedema after breast cancer treatment were divided into two groups. Women in the weight-lifting group received a one-year membership to a local gym. For the first 13 weeks, they participated in twice weekly, 90-minute supervised exercise sessions that included stretching, a cardiovascular warm-up, and abdominal and back exercises. The weight-lifting exercises involved low weights, and one to three new exercises were added at each session.

The number of sets increased from two to three, with 10 reps in each set, during the first five weeks. If the women felt OK, more weight was added.

After 13 weeks, women in the weight-lifting group continued twice-weekly exercise sessions on their own for an additional 39 weeks. By contrast, the women in the other group continued their normal exercise routine throughout the study period. All women wore a custom-fitted compression garment on their affected arm during their workouts.

Overall, the women who lifted weights experienced fewer exacerbations of their lymphedema, and they showed a reduction in symptoms compared to the women in the control group. Nineteen women in the control group had lymphedema exacerbations, compared to nine in the treatment group, the researchers report. A similar proportion of women in both groups showed an increase of 5 percent or more in their limb swelling.

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Kleinman-Barnett currently prescribes range-of-motion exercises, stretching, and massage to stimulate lymphatic flow in her patients. "I will now incorporate weight lifting using 2 to 3 pound weights, and slowly increase it, and teach them how to monitor themselves to be sure they are not increasing swelling," she said. Red flags that weight lifting may be making things worse include more swelling, heaviness, and pain in the arm, she said.

Dr. Marisa Weiss, the president and founder of the advocacy group Breastcancer.org, and the author of the forthcoming new edition of "Living Well Beyond Breast Cancer," said the new study is good news for two groups of women -- those who have lymphedema and those at risk of developing it. Health.com: Tips for staying hopeful if breast cancer returns

"For women who already have lymphedema, this is good news because we have not known how to get them back to moving and grooving again," said Weiss, who is the director of breast radiation oncology and breast health outreach at Lankenau Hospital in Wynnewood, Pennsylvania. "Our arms are essential to our ability to be physically active, and we haven't known how to advise these women in the past."

Lymphedema is more common after surgeries that remove most or all of the lymph nodes in the under arm area because there are few if any lymphatic drains left intact after such surgeries, she says. "If regular weight lifting with a sleeve in a supervised setting is OK for women with lymphedema, then it is reasonable for women with breast cancer treatment who are at risk of developing lymphedema to go back to some of the things they enjoyed in the past," she said.

Karen Strauss, a 50-year-old breast cancer survivor who developed lymphedema four months ago, is excited about the findings because she may be able to return to some of the exercises she did before developing breast cancer. Health.com: Can Twitter and Facebook help fight breast cancer?

"I used to do a whole workout when I went to the gym, but I have gotten away from it because I am afraid I would make things worse," said Strauss, a clinical social worker in Fort Lauderdale, Florida. "I have been afraid to do anything, but not anymore."

Strauss currently wears a compression sleeve and glove, gives herself light-touch massages, and does non-weight-bearing exercises to treat her lymphedema. But the new study results have convinced her to talk to her lymphedema specialist about adding light weights to the mix. Health.com: Find out how to run your first or fastest 5K or 10K